He says that Mercedes users, McLaren and Brawn, decided to block the deal.

Talking at the Motorsport Safety Fund’s Watkins Lecture at Autosport International, Newey says that the team wanted the engines because of the Mercedes teams’ performance advantage:

“The Mercedes engine enjoyed a good advantage over the rest of the field last year. The lap time difference was significant – several tenths of a second. And when you have to find that kind of performance from the chassis, that’s quite a big ask.”

“But in the end Brawn and McLaren blocked us from having the Mercedes engine.”

The team had also looked at using Cosworth engines for 2010, but decided to stay with Renault for the time being, despite reliability issues.